[llvm] r274699 - ThinLTO: Add test cases for promote+internalize.

Tue Jul 25 17:49:41 PDT 2017

On Tue, Jul 25, 2017 at 4:24 PM Peter Collingbourne <peter at pcc.me.uk> wrote:

> On Tue, Jul 25, 2017 at 2:29 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
>> Hey Peter,
>>
>> Bit of thread necromancy here - but I'm trying to change some things wrt
>> alias+linkonce_odr (going to make it behave like the alias+external case,
>> for simplicity, less duplication, and simplified debug info) & this test is
>> failing:
>>
>> My change causes none of the aliasees to be imported (not even those
>> linkonce_odr ones).
>>
>
> Is that a good idea? I would have thought that we'd want to go in the
> opposite direction and try to import more functions that use aliases. I
> believe that is blocked on support for available_externally aliases though
> (this thread has the most recent discussion I can find on that topic:
> http://lists.llvm.org/pipermail/llvm-dev/2017-January/109227.html).
>

Right, ultimately that's the right direction - this functionality though,
is a dead-end, it's not a stepping stone towards that outcome - and it gets
in the way (specifically it gets in the way of debug info, but also means
thinlto backend objects are larger than they need to be - by having
linkonce functions when they could be relying on the
linkonce-promoted-to-weak definition) without any specific reason to
believe the benefit (optimizing across aliases of linkonce_odr functions)
is significant.

>
> This causes -thinlto-action=internalize to fail ("-internalize will not
>> perform without -exportedsymbol").
>>
>
> Is it really failing because of that?
> http://llvm-cs.pcc.me.uk/tools/llvm-lto/llvm-lto.cpp#618
> Looks like it just prints a warning.
>

Yep, it prints a warning & then doesn't internalize anything/is a no-op, as
per the warning.

> It looks like if I fix this by passing -exported-symbol=main, nothing is
>> internalized (all the aliases are called from main) so it may defeat the
>> purpose of this test?
>>
>
> Right, if we export main then that would prevent us from internalizing
> anything across modules that is referenced by main, as we don't currently
> support cross-module internalization.
>

Not sure I follow that - it seemed to work (in the sense that saying main
was exported, nothing was internalized - which seems like the correct
answer to me, rather than "unsupported" (though unsupported could mean it
does that but breaks elsewhere - fair enough))

> (I don't really understand how this was working/what it was doing before,
>> though: What kept the aliasees alive if not the calls from main? Maybe a
>> record in the index saying "these are being used elsewhere" - but why isn't
>> there a similar record for the aliases that would've stopped them from
>> being internalized in the first place?)
>>
>
> I don't recall for sure but I believe that the point of that part of the
> test was to show that if no symbols are exported, the linkage changes
> applied by promote are unimportant because they are wiped out by a later
> internalize pass (which would internalize pretty much everything because
> nothing is exported).
>

Except there are exported symbols... - if there are no exported symbols
then internalize doesn't run so it wouldn't show/demonstrate anything?

> So I think the right change to make in that part of the test (if we wanted
> to go with your proposed change) would be to test that the remaining
> declarations are internal.
>
> Peter
>
>
>> Preciate any thoughts you have here,
>>
>> - Dave
>>
>>
>> On Wed, Jul 6, 2016 at 4:00 PM Peter Collingbourne via llvm-commits <
>> llvm-commits at lists.llvm.org> wrote:
>>
>>> Author: pcc
>>> Date: Wed Jul  6 17:53:02 2016
>>> New Revision: 274699
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=274699&view=rev
>>> Log:
>>> ThinLTO: Add test cases for promote+internalize.
>>>
>>> This tests the effect of both promotion and internalization on a module,
>>> and helps show that D21883 is NFC wrt promotion+internalization.
>>>
>>> Differential Revision: http://reviews.llvm.org/D21915
>>>
>>> Modified:
>>>     llvm/trunk/test/ThinLTO/X86/alias_import.ll
>>>     llvm/trunk/test/ThinLTO/X86/weak_resolution.ll
>>>
>>> Modified: llvm/trunk/test/ThinLTO/X86/alias_import.ll
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/ThinLTO/X86/alias_import.ll?rev=274699&r1=274698&r2=274699&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/test/ThinLTO/X86/alias_import.ll (original)
>>> +++ llvm/trunk/test/ThinLTO/X86/alias_import.ll Wed Jul  6 17:53:02 2016
>>> @@ -2,6 +2,7 @@
>>>  ; RUN: opt -module-summary %p/Inputs/alias_import.ll -o %t2.bc
>>>  ; RUN: llvm-lto -thinlto-action=thinlink -o %t.index.bc %t1.bc %t2.bc
>>>  ; RUN: llvm-lto -thinlto-action=promote -thinlto-index %t.index.bc
>>> %t2.bc -o - | llvm-dis -o - | FileCheck %s --check-prefix=PROMOTE
>>> +; RUN: llvm-lto -thinlto-action=promote -thinlto-index %t.index.bc
>>> %t2.bc -o - | llvm-lto -thinlto-action=internalize -thinlto-index
>>> %t.index.bc -thinlto-module-id=%t2.bc - -o - | llvm-dis -o - | FileCheck %s
>>> --check-prefix=PROMOTE-INTERNALIZE
>>>  ; RUN: llvm-lto -thinlto-action=import -thinlto-index %t.index.bc
>>> %t1.bc -o - | llvm-dis -o - | FileCheck %s --check-prefix=IMPORT
>>>
>>>  ;
>>> @@ -86,7 +87,45 @@
>>>  ; IMPORT-DAG: declare void @weakfuncWeakODRAlias()
>>>  ; IMPORT-DAG: declare void @weakfuncLinkonceODRAlias()
>>>
>>> -
>>> +; Promotion + internalization should internalize all of these, except
>>> for aliases of
>>> +; linkonce_odr functions, because alias to linkonce_odr are the only
>>> aliases we will
>>> +; import (see selectCallee() in FunctionImport.cpp).
>>> +; PROMOTE-INTERNALIZE-DAG: @globalfuncAlias = internal alias void
>>> (...), bitcast (void ()* @globalfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @globalfuncWeakAlias = internal alias void
>>> (...), bitcast (void ()* @globalfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @globalfuncLinkonceAlias = internal alias
>>> void (...), bitcast (void ()* @globalfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @globalfuncWeakODRAlias = internal alias
>>> void (...), bitcast (void ()* @globalfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @globalfuncLinkonceODRAlias = internal alias
>>> void (...), bitcast (void ()* @globalfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @internalfuncAlias = internal alias void
>>> (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @internalfuncWeakAlias = internal alias void
>>> (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @internalfuncLinkonceAlias = internal alias
>>> void (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @internalfuncWeakODRAlias = internal alias
>>> void (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @internalfuncLinkonceODRAlias = internal
>>> alias void (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @linkonceODRfuncAlias = alias void (...),
>>> bitcast (void ()* @linkonceODRfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @linkonceODRfuncWeakAlias = internal alias
>>> void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @linkonceODRfuncLinkonceAlias = internal
>>> alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @linkonceODRfuncWeakODRAlias = weak_odr
>>> alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @linkonceODRfuncLinkonceODRAlias = weak_odr
>>> alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @weakODRfuncAlias = internal alias void
>>> (...), bitcast (void ()* @weakODRfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @weakODRfuncWeakAlias = internal alias void
>>> (...), bitcast (void ()* @weakODRfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @weakODRfuncLinkonceAlias = internal alias
>>> void (...), bitcast (void ()* @weakODRfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @weakODRfuncWeakODRAlias = internal alias
>>> void (...), bitcast (void ()* @weakODRfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @weakODRfuncLinkonceODRAlias = internal
>>> alias void (...), bitcast (void ()* @weakODRfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @linkoncefuncAlias = internal alias void
>>> (...), bitcast (void ()* @linkoncefunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @linkoncefuncWeakAlias = internal alias void
>>> (...), bitcast (void ()* @linkoncefunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @linkoncefuncLinkonceAlias = internal alias
>>> void (...), bitcast (void ()* @linkoncefunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @linkoncefuncWeakODRAlias = internal alias
>>> void (...), bitcast (void ()* @linkoncefunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @linkoncefuncLinkonceODRAlias = internal
>>> alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @weakfuncAlias = internal alias void (...),
>>> bitcast (void ()* @weakfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @weakfuncWeakAlias = internal alias void
>>> (...), bitcast (void ()* @weakfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @weakfuncLinkonceAlias = internal alias void
>>> (...), bitcast (void ()* @weakfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @weakfuncWeakODRAlias = internal alias void
>>> (...), bitcast (void ()* @weakfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: @weakfuncLinkonceODRAlias = internal alias
>>> void (...), bitcast (void ()* @weakfunc to void (...)*)
>>> +; PROMOTE-INTERNALIZE-DAG: define internal void @globalfunc()
>>> +; PROMOTE-INTERNALIZE-DAG: define internal void @internalfunc.llvm.0()
>>> +; PROMOTE-INTERNALIZE-DAG: define internal void @linkonceODRfunc()
>>> +; PROMOTE-INTERNALIZE-DAG: define internal void @weakODRfunc()
>>> +; PROMOTE-INTERNALIZE-DAG: define internal void @linkoncefunc()
>>> +; PROMOTE-INTERNALIZE-DAG: define internal void @weakfunc()
>>>
>>>  define i32 @main() #0 {
>>>  entry:
>>>
>>> Modified: llvm/trunk/test/ThinLTO/X86/weak_resolution.ll
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/ThinLTO/X86/weak_resolution.ll?rev=274699&r1=274698&r2=274699&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/test/ThinLTO/X86/weak_resolution.ll (original)
>>> +++ llvm/trunk/test/ThinLTO/X86/weak_resolution.ll Wed Jul  6 17:53:02
>>> 2016
>>> @@ -7,6 +7,7 @@
>>>  ; non-prevailing ODR are not kept when possible, but non-ODR
>>> non-prevailing
>>>  ; are not affected.
>>>  ; RUN: llvm-lto -thinlto-action=promote %t.bc -thinlto-index=%t3.bc -o
>>> - | llvm-dis -o - | FileCheck %s --check-prefix=MOD1
>>> +; RUN: llvm-lto -thinlto-action=promote %t.bc -thinlto-index=%t3.bc
>>> -exported-symbol=linkoncefunc -o - | llvm-lto -thinlto-action=internalize
>>> -thinlto-module-id=%t.bc - -thinlto-index=%t3.bc
>>> -exported-symbol=linkoncefunc -o - | llvm-dis -o - | FileCheck %s
>>> --check-prefix=MOD1-INT
>>>  ; RUN: llvm-lto -thinlto-action=promote %t2.bc -thinlto-index=%t3.bc -o
>>> - | llvm-dis -o - | FileCheck %s --check-prefix=MOD2
>>>  ; When exported, we always preserve a linkonce
>>>  ; RUN: llvm-lto -thinlto-action=promote %t.bc -thinlto-index=%t3.bc -o
>>> - --exported-symbol=linkonceodrfuncInSingleModule | llvm-dis -o - |
>>> FileCheck %s --check-prefix=EXPORTED
>>> @@ -47,6 +48,7 @@ entry:
>>>    ret void
>>>  }
>>>  ; MOD1: define weak void @linkoncefunc()
>>> +; MOD1-INT: define weak void @linkoncefunc()
>>>  ; MOD2: define linkonce void @linkoncefunc()
>>>  define linkonce void @linkoncefunc() #0 {
>>>  entry:
>>> @@ -66,6 +68,7 @@ entry:
>>>  }
>>>
>>>  ; MOD1: define linkonce_odr void @linkonceodrfuncInSingleModule()
>>> +; MOD1-INT: define internal void @linkonceodrfuncInSingleModule()
>>>  ; EXPORTED: define weak_odr void @linkonceodrfuncInSingleModule()
>>>  define linkonce_odr void @linkonceodrfuncInSingleModule() #0 {
>>>  entry:
>>>
>>>
>>> _______________________________________________
>>> llvm-commits mailing list
>>> llvm-commits at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>>
>>
>
>
> --
> --
> Peter
>
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